Stent with segmented graft

ABSTRACT

A stent-graft comprising an expandable stent and a plurality of graft segments, each graft segment having a first end attached to the stent and a second end not attached to the stent. In one embodiment, the plurality of overlapped graft segments form a continuous conduit wherein each overlap between axially adjacent graft segments comprises a fluid-tight seal when the stent in the radially expanded configuration sandwiches the graft segments against a wall of a body lumen. In another embodiment, there are one or more discontinuities in the plurality of graft segments. The discontinuities may be aligned with branch lumens. The graft segments may be cut perpendicular to the stent-graft axis, or on a bias. A delivery system for and method of deploying the stent-graft are also claimed.

TECHNICAL FIELD

The present invention relates generally to endoluminal grafts or“stents” and, more specifically, to stent-graft combinations adapted tobe deployed without interrupting fluid flow during deployment.

BACKGROUND OF THE INVENTION

A stent is an elongated device used to support an intraluminal wall. Inthe case of a stenosis, a stent provides an unobstructed conduit througha body lumen in the area of the stenosis. Such a stent may also have aprosthetic graft layer of fabric or covering lining the inside and/oroutside thereof. Such a covered stent is commonly referred to in the artas an intraluminal prosthesis, an endoluminal or endovascular graft(EVG), or a stent-graft. A stent-graft may be used, for example, totreat a vascular aneurysm by removing the pressure on a weakened part ofan artery so as to reduce the risk of rupture. The term “endoluminaldevice” is often used to refer to any device implanted in a lumen,including stents, stent-grafts, vena cava filters, and the like.

Typically, an endoluminal device, such as a stent-graft deployed in ablood vessel at the site of a stenosis or aneurysm, is implantedendoluminally, i.e. by so-called “minimally invasive techniques” inwhich the device, restrained in a radially compressed configuration by asheath or catheter, is delivered by a delivery system or “introducer” tothe site where it is required. The introducer may enter the body from anaccess location remote from the treatment site, such as through thepatient's skin, or by a “cut down” technique in which the entry bloodvessel is exposed by minor surgical means. The term “proximal” as usedherein refers to portions of the stent or delivery system relativelycloser to the end of the delivery system that is remote from thetreatment site, whereas the term “distal” is used to refer to portionsfarther from the end that is remote from the treatment site.

When the introducer has been advanced into the body lumen to thedeployment location, the introducer is manipulated to cause theendoluminal device to be ejected from the surrounding sheath or catheterin which it is restrained (or alternatively the surrounding sheath orcatheter is retracted from the endoluminal device), whereupon theendoluminal device is expanded to a predetermined diameter at thedeployment location, and the introducer is withdrawn. Stent expansionmay be effected by spring elasticity, balloon expansion, or by theself-expansion of a thermally or stress-induced return of a memorymaterial to a pre-conditioned expanded configuration.

Stent-grafts are known in the art having a “wind-sock” design wherebythe graft is attached to the stent at only an upstream location on thestent, so that as the stent is deployed, endoluminal fluid can continueto flow between the stent and the graft, while the graft is suspendedlike a wind sock. Such designs avoid the pressure of obstructed bloodflow during deployment that may cause the prosthesis to migrate awayfrom its intended location or become longitudinally compressed. Anexemplary such stent-graft design is described in U.S. Pat. No.5,954,764 to Juan Parodi, incorporated herein by reference, which alsodescribes an exemplary device for deploying such a stent-graft design.Another deployment system for such a stent-graft design is described inU.S. patent application Ser. No. 09/337,120, titled LOW PROFILE DELIVERYSYSTEM FOR STENT AND GRAFT DEPLOYMENT AND METHOD FOR DEPLOYMENT, by CarlE. Yee, filed Jun. 21, 1999, assigned to the assignee of the presentinvention, and incorporated herein by reference.

The standard wind-sock stents known in the art, however, have drawbacksrelated to precision of deployment, stent flexibility once deployed, andcomplexity of the introducers used for deploying them. Thus, there isstill a need in the art for improved stent-graft designs that minimizedisruption of fluid flow during deployment, but also provide advantagesover designs currently known in the art.

SUMMARY OF THE INVENTION

One aspect of the invention comprises a stent-graft comprising anexpandable stent and a plurality of graft segments, each graft segmenthaving a first end attached to the stent and a second end not attachedto the stent. In one embodiment, the graft segments radially overlie thestent, forming one or more overlaps between axially adjacent graftsegments. Each graft segment second end may radially overlie the firstend of an axially adjacent graft segment, the graft segment first endmay radially underlie a second end of another axially adjacent graftsegment, or both. In one embodiment, the plurality of overlapped graftsegments form a continuous conduit wherein each overlap between axiallyadjacent graft segments comprises a fluid-tight seal when the stent inthe radially expanded configuration sandwiches the graft segmentsagainst a wall of a body lumen. In another embodiment, there are one ormore discontinuities in the plurality of graft segments.

All of the plurality of graft segments may have an equal length, or oneor more graft segments may be relatively shorter than one or more othergraft segments. The relatively shorter-length graft segments may bealigned with the curved or tortuous portion of the body lumen, or may bepositioned upstream of the one or more relatively longer graft segments.

Each of the one or more overlaps between axially adjacent graft segmentsmay comprise an overlap along an entire periphery of the stent-graft, orone or more of the overlaps may be along less than an entire peripheryof the stent-graft. Each graft segment may have opposite ends that areperpendicular to the central axis of the stent-graft, or one or more orall of the graft segments may be biased to the central axis.

The graft segment bias may create a discontinuity in the plurality ofgraft segments, such as for aligning with a branch lumen or forpermitting perfusion. A gap between axially adjacent graft segments mayalso be provided for creating a discontinuity in the plurality of graftsegments.

In one embodiment, the stent-graft is adapted for deployment inside abody lumen in a distal deployment location from a proximal accesslocation outside the body lumen, and the prosthesis comprises orconsists of a plurality of graft segments each having a distal end and aproximal end, an expandable stent underlying the graft, a plurality oflinks at or near the distal end of each graft segment for linking thestent and the graft segments together, and a lapped interface between atleast one pair of axially adjacent graft segments. The proximal end of adistal graft segment axially overlaps the distal end of a proximal graftsegment in each lapped interface.

In another embodiment, the stent-graft is adapted for deployment insidea body lumen having fluid therein that flows downstream from an upstreamlocation to a downstream location. Such a stent-graft comprises anexpandable stent and a plurality of graft segments overlying the stent.Each segment has an upstream end and a downstream end, and is linked tothe stent only at or near the upstream end. Each graft segment has adownstream end that overlaps the upstream end of an axially adjacentgraft segment, an upstream end overlaps the downstream end of an axiallyadjacent graft segment, or both. In other words, the stent-graftcomprises the stent and a first graft segment having an upstream end anda downstream end, the first graft segment attached to the stent only atthe first graft segment upstream end. The second graft segment has anupstream end and is attached to the stent only at the second graftsegment upstream end in a location on the stent that is upstream of thedownstream end of the first graft segment, such that the first graftsegment downstream end overlaps the first graft segment upstream end.

Another aspect of the invention is a delivery system for deploying astent-graft inside a body lumen having fluid therein that flowsdownstream from an upstream location to a downstream location. Thedelivery system comprises a stent graft having a compressedconfiguration and an expanded configuration, the stent-graft comprisingan expandable stent and a plurality of graft segments overlying thestent, each graft segment having a first end attached to the stent and asecond end not attached to the stent. The delivery system furthercomprises an outer sheath that overlies the compressed stent-graft andis retractable in the downstream direction. The delivery system mayfurther comprise a shaft mounted coaxially within the outer sheath and acatheter tip on the upstream end of the shaft, the shaft and thecatheter tip both optionally having a guidewire lumen therethrough.

Another aspect of the invention is a method for delivering a stent-graftinto a body lumen having an intraluminal fluid therein flowing in adownstream direction from an upstream location. The method comprisesintroducing a delivery system as described herein into the body lumenand retracting the outer sheath in the downstream direction such thatwhen a first graft segment is at least partially unsheathed, theintraluminal fluid flows in a first path through the stent and betweenthe downstream end of the first graft segment and the upstream end ofthe outer sheath. The fluid flows in this path until an upstream end ofa second graft segment is unsheathed sufficiently to cut off flowthrough the first path. The intraluminal fluid then flows through asecond path through the stent between the downstream end of the secondgraft segment and the outer sheath when the second graft segment iscompletely unsheathed. The method comprises continuing to retract theouter sheath until the stent-graft is fully deployed. In one embodiment,the plurality of graft segments overlap one another to create a fluidtight seal at each interface between overlapping graft segments,creating a continuous fluid conduit. In another embodiment, thestentgraft comprises one or more discontinuities and the body lumencomprises one or more branch lumens, the method comprising deploying thestent-graft so that the one or more discontinuities are aligned with theone or more branch lumens.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF DRAWING

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures:

FIG. 1 shows an exemplary stent-graft loaded in an exemplary deliverysystem, shown in partial longitudinal-section, after introduction into abody lumen, shown in longitudinal section;

FIG. 2 shows a complete longitudinal section of the delivery system andstent-graft of FIG. 1 after deployment of a first graft segment;

FIG. 3 shows a plan view of the delivery system and stent-graft of FIG.1 after deployment of two graft segments inside the lumen;

FIG. 4 depicts the delivery system and stent-graft of FIG. 3 afterdeployment of three graft segments;

FIG. 5 depicts the delivery system and stent-graft of FIG. 4 after fulldeployment of the stent-graft;

FIG. 6 shows a plan view of a stent-graft having unequal graft segmentsinside a longitudinal section of a lumen;

FIG. 7 shows a plan view of a stent-graft having graft segments withbiased ends inside a longitudinal section of a lumen having a branchlumen;

FIG. 8A shows a partial longitudinal section of a perpendicular graftsegment end being deployed;

FIG. 8B shows a partial longitudinal section of an upstream biased graftsegment end being deployed;

FIG. 8C shows a partial longitudinal section of a downstream biasedgraft segment end being deployed; and

FIG. 9 shows a plan view of stent-graft having a discontinuity betweentwo axially adjacent graft segments.

DETAILED DESCRIPTION OF INVENTION

Referring now to the drawing, wherein like reference numerals refer tolike elements throughout, FIGS. 1-5 show an exemplary stent-graft 10 ofthe present invention being deployed from an exemplary delivery system20 in a distal location in a body lumen 30 from a proximal locationoutside the body. Intraluminal fluid, such as blood in a vascularapplication, flows downstream in the direction of arrow A. Stent graft10 comprises an expandable stent 12 and a plurality of graft segments 14a-14 d radially overlying the stent. Each graft segment 14 a-14 d hasits respective distal, upstream end 16 a-16 d attached to the stent andits proximal, downstream end 18 a-18 d unattached to the stent. Thus, asshown in FIG. 2, as outer sheath 22 is retracted and graft segment 14 ais fully unsheathed, the intraluminal fluid can flow in a path alongarrow B through stent 12 and between graft 14 a and the upstream end ofouter sheath 22.

As shown in FIG. 3, graft segment 14 b radially overlaps axiallyadjacent graft segment 14 a along overlapped portion 19 b. Inparticular, the downstream end 18 a of graft segment 14 a radiallyoverlies upstream end 16 b of graft segment 14 b. Similarly, theupstream end 16 b of graft segment 14 b radially underlies downstreamend 18 a, while the downstream end 18 b of graft segment 14 b radiallyoverlies upstream end 16 c of graft segment 14 c. Thus, each graftsegment has a downstream end overlying the upstream end of an axiallyadjacent graft segment (i.e. segments 14 a-14 c), an upstream endunderlying the downstream end of another axially adjacent graft segment(i.e. segments 14 b-14 d) or both (i.e. 14 b and 14 c).

The plurality of overlapped graft segments shown in FIGS. 1-5 thus forma continuous conduit, each overlap between axially adjacent graftsegments forming a fluid-tight seal as radially expanded stent 12sandwiches graft segments 14 a-d against wall 32 of body lumen 30.

The graft may be a braided or non-braided graft, and may comprise anygraft material known in the art. Suitable graft materials include, butare not limited to, polyethyleneterepthalate (PET), polyetheretherketone(PEEK), polysulfone, polytetrafluroethylene (PTFE), expandedpolytetrafluroethylene (ePTFE), fluorinated ethylene propylene (FEP),polycarbonate urethane, a polyolefin (such as polypropylene,polyethylene, or high density polyethylene (HDPE)), silicone, andpolyurethane. Yarns for braided grafts may comprise monofilaments ormultifilament yarns, either with round or non-round cross-section, andmultifilament yarns may comprise twisted or untwisted filaments.

The stent may comprise any material known in the art, including but notlimited to self-expanding metals such as nitinol, balloon-expandablematerials such as stainless steel, or even non-metals, such as polymermaterials. The stent may also comprise a hybrid self-expanding,balloon-expandable design, having at least one superelastic section andat least one plastically deformable section, such as but not limited tothose described in U.S. patent application Ser. No. 09/702,226, bySteven E. Walak, filed Oct. 31, 2000, assigned to the common assignee ofthis invention, and incorporated herein by reference. The stent maycomprise any stent architecture known in the art, such as but notlimited to filamentary or cut tube architectures, including filamentarystents that are wound or braided along their entire length, or hybridbraided/wound stents, such as are described in U.S. patent applicationSer. No. 09/442,165, filed Nov. 16, 1999, by Chouinard et al., assignedto the assignee of this invention and incorporated by reference.

A portion of the underlying stent may be uncovered by graft material atthe proximal and/or distal ends of the stent, such as uncovered portion13 of stent 12 shown in FIGS. 2-5. Such an uncovered stent portiontypically allows intraluminal tissue growth (not shown) to provideadditional anchoring for the stent as is known in the art. Even wherethere is no uncovered stent portion at the proximal end, it is desirablefor the proximal end of the proximal-most graft (such as graft 14 dshown in FIG. 5) not to extend proximally any further than the proximalend of the underlying stent. The ability to better control the terminallocation of the proximal end of the graft relative to the proximal endof the stent is one advantage of the segmented covering as compared tonon-segmented “wind-sock” designs, because the unattached portion of thegraft is smaller in the segmented design. Accordingly, placement of theproximal end of a segmented graft is easier to predict than placement ofthe proximal end of a non-segmented graft, taking into accountforeshortening of the stent and other factors.

As shown in FIG. 1, stent 12 comprises a hybrid stent having anon-braided distal end section 15 and a braided midsection 17, such as ahybrid wound/braided design as described in the '165 application. Theterm “midsection” as used herein refers to any portion of thestent-graft between the proximal and the distal ends. Although hybridstents in which the wound end section and braided midsection areconnected by one or more continuous filaments running through bothsections as disclosed in the '165 application are advantageous, theinvention is not limited to such a configuration, nor is the inventionlimited to any particular type of stent architecture. The end sectionmay comprise ends that are freely terminating or twisted together, oratraumatic ends such as continuous ends or wound ends, all of which areknown in the art. Architectures with continuous ends, for example, aredescribed in publication WO 99/25271 to Wolfgang et al., incorporatedherein by reference. End section 15 is not limited to any particulararchitecture, however, and may comprise any architecture known in theart, including the same architecture as midsection 17.

The attachments or links (not shown) between each graft segment 14 a-14d and stent 12 may comprise any type of attachment known in the art,including but not limited to, sutures, staples, adhesive, wire, a sewnseam, and any combination or equivalent thereof.

The stent-graft of this invention may be useful in any number ofapplications in any body lumen, vascular or non-vascular. In particular,however, it is useful for treatment of thoracic aortic aneurysms (TAA).The segmented graft design is particularly useful for TAA applicationsbecause it overcomes the imprecision of existing systems that occludeblood flow during deployment and thus are prone to deployment migration.The pulsatile blood flow in the thoracic aorta may make TAA stent-graftsparticularly subject to such migration. The segmented covering asdescribed herein allows blood to flow through each graft segment untilthe next segment is deployed. The segmented graft design is alsoadvantageous for deployment in any tortuous or curved lumen, thus alsoproviding further advantage for TAA applications.

In stent-graft 10 shown in FIGS. 1-5, the plurality of graft segmentscomprise a continuous fluid conduit wherein each pair of overlappinggraft segments comprises an overlap along a complete periphery of thegraft segment, each graft segment has square edges perpendicular to thecentral axis of the stent-graft (which runs coaxial with shaft 24 shownin FIGS. 1-5), and all the graft segments are of approximately equallength. Any number of variations from this design are possible, however,well-within the scope of this invention. For example, the graft segmentsmay be of unequal length, as illustrated in FIG. 6. One advantage ofmaking graft segments of unequal length is that a section of thestent-graft having more graft segments may have more flexibility than asection with fewer graft segments. Thus, portions of a stent-grafthaving short graft segments may be particularly well-suited fordeployment in curved or tortuous regions of a body lumen.

Stent-graft 610 shown in FIG. 6 balances one advantage of the segmentedgraft, namely that it allows blood to continue to flow duringdeployment, against one disadvantage, namely that each overlap betweengrafts provides a seam that may potentially leak. Stent-graft 610 hasupstream graft segments 614 a and 614 b that are relatively shorter thandownstream graft segments 614 d and 614 e. Graft segments ofintermediate length, such as segment 614 c, may be provided between theupstream and downstream graft segments, creating a gradient in graftsegment length from upstream to downstream ends of the stent-graft.Relatively shorter upstream graft segments 614 a and 614 b provide lessresistance to blood flow at the beginning of deployment when very littleof stent-graft 610 has been anchored and it is particularly prone tomigration. Relatively longer downstream graft segments 614 d and 614 eprovide fewer seams near the end of deployment when the stent is alreadypartially anchored and more resistant to migration.

In another stent-graft embodiment, the graft segments and/or the stentmay be cut on a bias rather than having square edges. In particular, thegraft segments may be cut on a bias in such a way as to leave adiscontinuity in the stent-graft to accommodate branch lumen. Forexample, as shown in FIG. 7, lumen 730 has a branch lumen 734, andstent-graft 700 has a discontinuity 740 of graft covering aligned withthe branch lumen. Discontinuity 740 is formed by the biased downstreamend 718 b of graft segment 714 b and opposingly-biased upstream end 716c of graft segment 714 c. By “opposingly-biased” it is meant that if therelationship between the upstream end and a plane P perpendicular to thecentral axis of the stent-graft is a positive angle, such as α, then therelationship between the downstream end and plane P is a negative angle,such as −α. Such opposingly-biased graft segments that create adiscontinuity inherently overlap each other over less than a fullperiphery of the graft segment. Accurate placement of discontinuity 740may be facilitated by the use of radiopaque markers as are known in theart. Acuurate placement of the discontinuity may be further facilitatedby the use of non-foreshortening or lesser-foreshortening stentarchitectures as are known in the art, or by the use of specialdeployment devices for the deployment of foreshortening endoluminaldevices, such as are described in U.S. patent application Ser. No.10/115,669, titled DELIVERY SYSTEM AND METHOD FOR DEPLOYMENT OFFORESHORTENING ENDOLUMINAL DEVICES, filed by James Weldon and IlyaYampolsky on Apr. 4, 2002, and incorporated herein by reference.

Although the embodiment shown in FIG. 7 depicts angles α and −α with thesame absolute value, the angles may have different absolute values.Overlapping grafts may also have a bias in the same direction (bothpositive, or both negative), with enough difference in the bias to forma discontinuity. It should be noted that a discontinuity may be providedin a graft by other means, such as merely by cutting out a notch orother type of opening of any shape at the end or middle of a graftsegment.

Even where it is not desired to have a discontinuity in the plurality ofgraft sections, the grafts may be biased, such as to create anelliptical attachment periphery that is greater than the circularattachment periphery provided by a perpendicular end. A largerperipheral attachment area provides greater attachment strength. Biasedgraft segments may be particularly advantageous for maximizing thepercentage of time during deployment that blood can flow through thestent-graft without obstruction. For example, as illustrated in FIG. 8A,perpendicularly-cut graft segment 814 b ₁ cuts off flow betweendownstream end 818 a ₁ of graft segment 814 a ₁ and outer sheath 822once the underlying stent becomes sufficiently expanded, and does notallow flow again until graft segment 814 b ₁ is completely unsheathed.By comparison, a biased graft segment 814 b 2 allows blood to flowlonger through path C before it is cut off when the downstream-mostportion of upstream end 816 b ₂ finally deploys, as shown in FIG. 8B.The biased design also allows blood flow to be reestablished soonerthrough path D when the upstream-most portion of downstream end 818 b 2of segment 814 b ₂ is unsheathed, as shown in FIG. 8C.

In yet another embodiment, shown in FIG. 9, stent-graft 900 may have adiscontinuity in the succession of graft segments created by space 940between axially adjacent graft segments 914 b and 914 c. Such adiscontinuity may be particularly advantageous to accommodate lumenssuch as lumen 930 having a plurality of branch lumens 934 and 936.

Delivery system shown in FIGS. 1-5 comprises stent graft 10, outersheath 22, shaft 24, and catheter tip 26 attached to the shaft. Shaft 24and catheter tip 26 may have lumens (not shown) therein, such as anaxial lumen, for accommodating a guidewire (not shown) as is commonlyknown in the art. The delivery system of the present invention may beused with or without a guidewire. One advantage of the delivery systemembodiment shown in FIGS. 1-5 is that the inside portion that actuallyis introduced into the body lumen is simple, consisting of essentiallynothing more than the components shown and described herein, with theguidewire and guidewire lumens in shaft 24 and 26 being optional. Such asimple design avoids the profile-adding multiple sheaths or othercomplexities of other delivery systems known in the art. Of course, thedelivery system may have additional elements not shown herein, as areknown in the art. In particular, the delivery system may compriseelements such as luer fittings and the like at the proximal end of thedelivery system as are known in the art, that, while in many casesessential to stent delivery procedures generally, are not essential tothe discussion herein.

In addition to the structural aspects of the invention, one aspect ofthe invention is a method for delivering a stent-graft of the typediscussed herein into a body lumen. Such a method comprises, withrespect to FIGS. 1-5, introducing a delivery system 20 into the bodylumen 30, the delivery system comprising stent-graft 10 in thecompressed configuration and outer sheath 22 overlying the stent graft,as shown in FIG. 1. Outer sheath 22 is retracted in the downstreamdirection such that when first graft segment 14 a is completelyunsheathed, the intraluminal fluid flows in path B through stent 12between the sheath and the downstream end 18 a of graft segment 14 auntil upstream end 16 b of graft segment 14 b is unsheathed sufficientlyto cut off flow through path B. The intraluminal fluid then flowsthrough a second path (not shown) through stent 12 between sheath 22downstream end 18 b of the graft segment 14 b and the sheath, once graftsegment 14 b is completely unsheathed. The method comprises continuingto retract outer sheath 22 until stent-graft 10 is fully deployed. Inthe embodiment shown in FIGS. 1-5, the plurality of graft segments 14a-d overlap one another to create a fluid tight seal at each interfacebetween overlapping graft segments, creating a continuous fluid conduit.In other stent-graft embodiments, such as shown in FIGS. 7 and 9, openareas between axially adjacent graft segments may be aligned with one ormore branch lumens.

Although illustrated and described herein with reference to certainspecific embodiments, the present invention is nevertheless not intendedto be limited to the details shown. Rather, various modifications may bemade in the details within the scope and range of equivalents of theclaims and without departing from the spirit of the invention.

1. A stent-graft comprising: a single continuous expandable stent of aparticular length having a radially compressed configuration and aradially expanded configuration, the stent defining a single continuouslumen with a larger diameter in the radially expanded configuration thanin the radially compressed configuration; and a plurality of discreteand separate grafts in series, each graft lining a different portion ofthe expandable stent, as determined by being longitudinally displacedalong the particular length, and having a first distal upstream endattached to the stent and a second proximal downstream end not attachedto the stent, wherein the grafts radially overlie the stent and at leasttwo axially adjacent grafts partially overlap one another to form anoverlapped portion on the single continuous expandable stent.
 2. Thestent-graft of claim 1, wherein each of the plurality of grafts has atleast one end that overlaps or is overlapped by an end of an axiallyadjacent graft.
 3. The stent-graft of claim 1, wherein the stentcomprises a self-expanding material.
 4. The stent-graft of claim 3,wherein the self-expanding material comprises nitinol.
 5. Thestent-graft of claim 1, wherein the stent comprises a balloon-expandingmaterial.
 6. The stent-graft of claim 5, wherein the balloon-expandablematerial comprises stainless steel.
 7. The stent-graft of claim 1,wherein the graft comprises a material selected from the groupconsisting of: polyethyleneterepthalate (PET), polyetheretherketone(PEEK), polysulfone, polytetrafluroethylene (PTFE), expandedpolytetrafluroethylene (ePTFE), fluorinated ethylene propylene (FEP),polycarbonate urethane, a polyolefin, silicone, and polyurethane.
 8. Thestent graft of claim 7, wherein the graft comprises a polyolefm selectedfrom the group consisting of: polypropylene, polyethylene, or highdensity polyethylene (HDPE).
 9. The stent-graft of claim 1, wherein thestent-graft is adapted for treatment of a thoracic aortic aneurysm. 10.A stent-graft comprising: a single continuous expandable stent of aparticular length having a radially compressed configuration and aradially expanded configuration, the stent defining a single continuouslumen with a larger diameter in the radially expanded configuration thanin the radially compressed configuration; and a plurality of discreteand separate graft segments in series, each graft segment lining adifferent portion of the expandable stent, as determined by beinglongituinally displaced along the particular length, and giving a firstdistal end attached to the stent and a second proximal end not attachedto the stent wherein the plurality of graft segments comprises one ormore relatively shorter length graft segments and one or more relativelylonger length graft segments and wherein the grafts radially overlie thestent and at least two axially adjacent grafts partially overlap oneanother to form an overlapped portion on the single continuousexpandable stent.
 11. The stent-graft of claim 10, wherein thestent-graft is adapted for deployment in a body lumen having a curved ortortuous portion with one or more relatively shorter-length graftsegments positioned to align with the curved or tortuous portion of thebody lumen.
 12. A stent-graft comprising: a single continuous expandablestent of a particular length having a radially compressed configurationand a radially expanded configuration, the stent defining a singlecontinuous lumen with a larger diameter in the radially expandedconfiguration than in the radially compressed configuration; and aplurality of discrete and separate grafts in series, each graft lining adifferent portion of the expandable stent, as determined by beinglongitudinally displaced along the particular length, and having a firstdistal end attached to the stent and a second proximal end not attachedto the stent, wherein at least a portion of the stent between at leasttwo of the plurality of grafts is not radially overlaid by the at leasttwo of the plurality of grafts.
 13. The stent-graft of claim 12, whereinthe portion of the stent that is not radially overlaid by a graftsegment is an end of the stent adapted to be positioned upstreamrelative to the rest of the stent-graft in a body lumen having fluidflowing downstream from an upstream location.
 14. The stent-graft ofclaim 1, wherein the overlap extends along less than an entire peripheryof the stent-graft.
 15. The stent-graft of claim 1, wherein thestent-graft has a central axis and at least one graft has at least oneend that has a bias to the central axis.
 16. A stent-graft comprising: asingle continuous expandable stent of a particular length having aradially compressed configuration and a radially expanded configuration,the stent defining a single continuous lumen with a larger diameter inthe radially expanded configuration than in the radially compressedconfiguration; and a plurality of discrete and separate grafts inseries, each graft lining a different portion of the expandable stent,as determined by being longitudinally displaced along the particularlength, and having a first end attached to the stent and a second endnot attached to the stent, wherein the stent-graft has a central axisand at least one graft has at least one end that has an angular bias tothe central axis, wherein the angular bias creates a discontinuitybetween two axially adjacent grafts that partially overlap.
 17. Astent-graft comprising a single continuous expandable stent of aparticular length and a plurality of discrete and separate graftsegments in series, each graft segment lining a different portion of theexpandable stent, as determined by being longitudinally displaced alongthe particular length, and having a first distal end attached to thestent and a second proximal end not attached, wherein the stent-grafthas a central axis and at least one graft segment has at least one endthat has an angular bias to the central axis, wherein the angular biascreates an opening between two axially adjacent graft segments thatpartially overlap, the opening defined by a first graft segment having afirst angular bias and a second graft segment having a second angularbias not equal to the first bias.
 18. The stent-graft of claim 17,wherein the second bias opposes the first bias.
 19. The stent-graft ofclaim 18 wherein the second bias is approximately equal in absolutevalue to the first bias.
 20. A stent-graft comprising: a singlecontinuous expandable stent of a particular length having a radiallycompressed configuration and a radially expanded configuration, thestent defining a single continuous lumen with a larger diameter in theradial expanded configuration than in the radially compressedconfiguration; and a plurality of discrete and separate graft segmentsin series, each graft segment lining a different portion of theexpandable stent, as determined by being longitudinally displaced alongthe particular length, and having a first distal end attached to thestent and a second proximal end not attached wherein the stent-graftcomprises at least one gap between axially adjacent graft segments,creating a discontinuity in the plurality of graft segments, wherein atleast one of the axially adjacent graft segments partially overlaps withanother graft segment upstream or downstream from the at least one gap.21. A stent-graft comprising: a single continuous expandable stent of aparticular length having a radially compressed configuration and aradially expanded configuration, the stent defining a single continuouslumen with a larger diameter in the radially expanded configuration thanin the radially compressed configuration; and a plurality of discreteand separate graft segments in series, each graft segment lining adifferent portion of the expandable stent, as determined by beinglongitudinally displaced along the particular length, and having a firstdistal end attached to the stent and a second proximal end not attachedto the stent wherein the plurality of graft segments has at least onediscontinuity comprising an opening between axially adjacent graftsegments in the plurality of graft segments, wherein at least one of theaxially adjacent graft segments partially overlaps with another graftsegment upstream or downstream from the at least one discontinuity. 22.The stent-graft of claim 21, wherein the stent-graft is adapted fordeployment in a body lumen having at least one branch and thediscontinuity is positioned to align with the branch.
 23. A stent-graftadapted for deployment inside a body lumen in a distal deploymentlocation from a proximal access location outside the body lumen, thestent-graft comprising: a single continuous expandable stent of aparticular length underlying a plurality of discrete and separate graftsegments, the stent having a radially compressed configuration and aradially expanded configuration, the stent defining a single continuouslumen with a larger diameter in the radially expanded configuration thanin the radially compressed configuration; the plurality of discrete andseparate grafts being arranged in series, each graft segment lining adifferent portion of the expandable stent, as determined by beinglongitudinally displaced along the particular length, and having a firstdistal upstream end attached to the stent and a second proximaldownstream end not attached to the stent; a plurality of links at ornear the first distal upstream end of each graft segment for linking thestent and the graft segments together; and a lapped interface between atleast one pair of longitudinally adjacent graft segments in which thesecond proximal downstream end of a distal graft segment partiallyaxially overlaps the first distal upstream end of a proximal graftsegment to create a discontinuity between the axially adjacent graftsegments.
 24. The stent-graft of claim 23, wherein the stent-graftconsists essentially of the plurality of graft segments, the expandablestent, the plurality of links, and the lapped interfaces between thegraft segments.
 25. A stent-graft adapted for deployment inside a bodylumen having fluid therein that flows from an upstream direction to adownstream direction, the stent-graft comprising: a single continuousexpandable stent of a particular length having a radially compressedconfiguration and a radially expanded configuration, the stent defininga single continuous lumen with a larger diameter in the radiallyexpanded configuration than in the radially compressed configuration; aplurality of discrete and separate grafts in series overlying the stent,each graft lining a different portion of the expandable stent, asdetermined by being longitudinally displaced along the particularlength, each graft having an upstream end and a downstream end andlinked to the stent only at or near the upstream end with the downstreamend being not attached to the stent, wherein for each graft (a) thedownstream end partially overlaps the upstream end of a first axiallyadjacent graft, (b) the upstream end partially overlaps the downstreamend of a second axially adjacent graft, or (c) both.
 26. A stent-graftadapted for deployment inside a body lumen having fluid therein thatflows from an upstream direction to a downstream direction, thestent-graft comprising: a single continuous expandable stent of aparticular length having a radially compressed configuration and aradially expanded configuration, the stent defining a single continuouslumen with a larger diameter in the radially expanded configuration thanin the radially compressed configuration; a first graft having anupstream end and a downstream end, the first graft attached to the stentonly at the first graft upstream end and the first graft downstream endnot attached to the stent; and a second graft, discrete and separatefrom the first graft, the first and second grafts lining differentportions of the expandable stent, as determined by being longitudinallydisplaced along the particular length, the second graft having anupstream end and attached to the stent only at the second graft upstreamend in an axial location that is upstream of the downstream end of thefirst graft, such that the first graft downstream end partially overlapsthe second graft upstream end, and the second graft downstream end isnot attached to the stent.
 27. The stent-graft of claim 1, wherein thegrafts radially underlie the stent.
 28. The stent-graft of claim 1,wherein at least one of the plurality of separate grafts has a lengthdifferent from the remainder of the plurality of separate grafts.